A0 A 2 526 COMPUTED SURVFY SPECTRA Of 2-5 MICRON ATMOSPHERIC I/IARSORPTInN(U) NAVAL RESEARCH LAB WASHINGTON DCD H lESLIE [I AL. 31 AUG 83 NRL-MR-5168

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MICROCOPY RESOLUTION TEST CHAART

NATIONAL 9UREAU OF STANARS 63A

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NiL Measdum Reot 5168

Computed Survey Spectra of 2.5p Atmospheric AbsorptionD. H. LESLIE AND P. S. LEBOw

Appld Optics BrachOptical Sciences Division

August 31, 1983

DTICELECTE

NV " NN " ""88 0SEP 16 63

88 09 15066--4~~~..... ..... .- !-~ ~ ~ .

SECIURITY C.ASSIVICA'ON% OF T."S PAGE 'Wh.n . En,.,d)

REPORT DOCUMENTATION PAGE READ INSTRUCTIONSBEFORE COMPLETING FORMIREPORT1 NIJMBEP 2. GOVT ACCESSION NO. 3. PEC PEN4T'S CATA60OG NUMUER

NRL Memorandum Report 5168 14D-0I13,2 52C&__________

4. 11IT LE 'sod S.bit I.) 5 TYPE OF REPORT & PERICO COVEREC

COMPUTED SURVEY SPECTRA OF 2-5 .iInterim report on a continuingATMOSPHERIC ABSORPTION I NRL problem.

6b. PERFORMING 04G. REPORT NUNSEX

7. AUTiMO*(., I CON"RAC? OR GRANT NUMUERII'.)

D. H. Leslie and P. S. Lebow

S. PERFORMINiG OIRGANIZAIIONd NAME ANC) AOORESS 0C. PROGRAM ELE ENT. PROJECT, TASKAREA A OI .NI UIR

Optical Sciences Division WOK NT68NCM

Naval Research Laboratory R6-4-0 517--Washington, DC '20375 RF6PO428T 65A171A-

I.CONTROLLING OFFICE NAME ANO LOORESS'2 CO AT

Naval Research Laboratory August 31, 1983Washington, DC 20375 1 13. MUER OF PAGES

14. MONITORING AGENCY %AMC A AOORESS(I( 4ij.,.., ft,... C..I-111-0 OHfiI) is, SECURITY CLASS. (of this oport)~

IS&. OECLASSIFPICATiONOOWNGRAOINGSCP490ULE

16. OI5T11IUUTION STATEMENT (of this Revort)

Approved for public release; distribution unlimited.

17. OISTRIUUTION STATEMENT 'of fho obsI,ow - ... ~d 1. Wloe* 20. It diff....t Most. Roe. P11 xoA1

I0. SUPPLEMENTARY NOTES

~a Distributions/__

Availability Codes

It. KEY WOROS (Cotimi n. 1-0 ,**,ddo It nscoossm aid ldertily by block itsab.,)

are presented covering the wavelength region 2-5 . The 1980 AFGL atmospheric absorptionparameter compilation was employed with a mid-latitude, sea-level atmosphericmoe

DD 1473 EDITIONi OF I NOV 69 15 O§SOLETEt

SIR 002-01-6601SECURITY CLASSIFICATION OF TNIS PAGE (Moo. bete 9001181')

COMPUTED SURVEY SPECTRA OF 2-5Aj ATMOSPHERIC ABSORPTION

This report presents computed spectra of atmospheric absorption in the 2-5 im region. The spec-

tra collected here followed from a request for detailed information on narrow transmission windows.

The recent availability of tunable laser sources at 2-5 Am, including F-center lasers and downshifted

Raman devices, has renewed interest in narrow atmospheric transmission windows.

The spectra in Figs. 3-77 present molecular absorption coefficient (km - ) vs wavenumber (cm-').

where v(cm -t ) - 104 x X-Am). Aerosol scattering and absorption are not considered here. The

standard midlatitude-summer sea-level atmosphere is assumed, and described in Table 1. The water

vapor standard isotopic ratio HDO/H 20 - 0.030% is assumed.

Table I - MidLatitude Summer Sea-LevelAtmospheric Parameters

Molecular Pressure (torr) Concentration (ppm)

H20 14.26 1.88 x 104CO2 0.251 330

03 2.3 x 10-1 0.030N20 2.1 x 10-4 0.276CO 5.7 x 10- 5 0.075CH 4 1.2 x 10-1 1.5802 159.6 2.10 x 101N2 585.9 7.7 x 101

NOTE: Temperature - 22.9"C

The calculations were performed using our HITRAN code with the 1980 AFGL line compila-

tion. (1 2) The plots were made on a Versatek plotter at 100 points per inch resolution. Since each plot

is 40 cm - ' long across 7 inches, the effective wavenumber resolution is approximately 0.057 cm - 1 per

point. At sea level almost all absorption lines are pressure broadened to a HWHM greater than 0.05

cm -1 . The plot parameters were chosen to maximize the number of wavenumbers per plot panel,

without undersampling the true spectrum. The user of these survey spectra is cautioned to pay atten-

t b~

tior: to the vertical scale. each panel is self-scaling so some plots cover 2 decades where others cover as

much as 6 decades of absorption coefficient.

The 1982 AFGL listing has recently been released, 3) but no significant changes have been made

in the 2-5 jm region for the molecules considered here. Areas of uncertainty remain in the specific

correction needed for the sub-Lorentz CO 2 lineshape,( 4.5) and the BurchO6 ) vs White(7 ) 3.3-4.2 Am

water continuum absorption model.

Table 2 - Spectral Plot Parameters

Lineshape: Lorentz with ±20 cm - I bound

Self-to-Foreign Broadening: (1)

Ratio: yV/yF Temperature Coefficient y 7 TH20 5.0 0.62CO 2 1.3 0.5803 1.0 0.50N20 1.24 0.50CO 1.02 0.50CH 4 1.3 0.5002 1 1.0 0.50

NOTE: Water Vapor Continuum 2350 - 2800 cm- 1(5.6)Nitrogen continuum 2080 - 2740 cm

- 1 (5. 8)

CO, sub-Lorentz lineshape (4)

The spectral plot parameters are summarized in Table 2. The two continuum absorption contribu-

tions are well documented in the literature. The line-by-line summation was carried out to ±20 cm - t

from the plotted frequency. The correction to the CO2 spectra to account for the sub-Lorentz line

shape is-described in Fig. I and Eq. (1) below:

k (vo) - X ( - vo) kL (o) (1)

where

kL (Y) - I -YSk r (V - V0 )2 + y 2

and X (v - v0) is given in Fig. 1.

A broad-band transmittance plot for a 1 km path was produced using LOWTRAN-5b with the

above atmosphere and no aerosols (9). This is given in Fig. 2 and is useful for a quick glance at the

2

same region covered by the 75 high-resolution absorbance plots. The effective spectral resolution of

Fig. 2 is 20 cm-1.

1.0

0.8

0.6x

0.4

0.2

0.00 5 10 15 20

It - Vol cm- 1

Fig. I - X function in Eq. (1) used for CO2 sub-Lorentz lineshape

.. ,.... .... i.... ,.... ,..... '.., .... ,... ., ... .... .. .I ..I.eT .0

ANSM .O

S .40

.26-

2606 2406 200 3200 3666 4666 4400 460WAVEMJER

Fit. 2 - LOWTRAN-5 I km mid-latitude summer sea-level transmittance 5-2 #m

3

--

REFERENCES

1. R.A. McClatchey, W.S. Benedict, S.A. Clough, D.E. Burch, R.F. Calfee, K. Fox, L.S. Rothman,

J.S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Air

Force Cambridge Research Laboratories, Bedford, Massachusetts, January 1973.

2. L.S. Rothman, "AFGL Atmospheric Absorption Line Parameters Compilation 1980 Version,"

Applied Optics 20, 791-795 (1981).

3. L.S. Rothman, R.R. Gamache, A. Barbe, A. Goldman, J.R. Gillis, L.R. Brown, R.A. Toth, J.M.

Flaud, and C. Camy-Peyret, "AFGL Atmospheric Absorption Line Parameters Compilation: 1982

Edition," Applied Optics 22, 2247-2256 (1983).

4. D.E. Burch. D.A. Gryvnak, R.R. Patty, and C.E. Bartky, "Absorption of Infrared Radiant Energy

and CO2 and H20, IV. Shapes of Collision-Broadened CO2 Lines," J. Opt. Soc. Am. 59, 267-280,

1969.

5. P.L. Roney, F.D. Findlay, A. Blanchard, M.W.P. Cann, and R.W. Nicholls, "Atmospheric

Transmittance in the Region near the 4.3 jam Band Head of C0 2," Optics Letters 6, 153, (1981).

6. D.E. Burch, D.A. Gryvnak, and J.D. Pembrook, "Investigation of the Absorption of Infrared

Radiation by Atmospheric Gases: Water, Nitrogen, Nitrous Oxide," AFCRL-71-0124, Hanscom

AFB, MA (1971).

7. W.R. Watkins, K.O. White, L.R. Bower, and B.Z. Sojka, "Pressure Dependence of the Water

Vapor Continuum Absorption in the 3.5-4.0 m Region," Applied Optics 18, 1149-1160 (1979).

8. M.M. Shapiro and H.P. Gush, "The Collision-Induced Fundamental and First Overtone Bands of

Oxygen and Nitrogen," Canadian Journal of Physics 44, 949-963, 1966.

4

9. F.X Kneizys, E.P. Shettle, WO0. Gallery, H.J. Chetwynd, Jr., L.W. Abreu, J.E.A. Selby, R.W.

Fenn. and R.A. McClatchey, Atmospheric Transmittance/Radiance: Computer Code LOWTRAN 5,

AFGL-TR-80-0067, Air Force Geophysics Laboratory, Hanscom AFB, Massachusetts. 1980.

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